Dissertations / Theses: 'Evolution of magma'

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Wyk, de Vries Benjamin van. "Tectonics and magma evolution of Nicaraguan volcanic systems." Thesis, Open University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577137.

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Barr, Jay Arthur. "Primitive magmas of the Earth and Moon : a petrologic investigation of magma genesis and evolution." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62493.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010.
"September 2010." Cataloged from PDF version of thesis.
Includes bibliographical references.
Field studies, major and trace element geochemistry, isotopes, petrography, phase equilibrium experiments and thermodynamics are used investigate and understand primitive melts from the Earth and the Moon. Chapter 1 investigates spinifex orthopyroxene compositions from the komatiites of Commondale, South Africa, and uses phase equilibrium experiments to illustrate that the Commondale Komatiites were hydrous magmas when they were emplaced. Hydrous komatiites provide evidence for the existence of subduction zone volcanism during the Archean, and decreases the temperature required to explain komatiites volcanism, which is the major physical evidence used to determine the mantle potential temperature of the Archean. Chapter 2 uses phase equilibrium experiments investigate the origin of the Apollo 15 green glasses from the Moon. Garnet-lherzolite saturated experiments are used to calibrate a melting algorithm used to estimate the chemical compositions of melts of a primordial lunar mantle. Mixing models are used to reproduce the Apollo 15 green glass compositions. These models are consistent with primordial melts assimilating late stage lunar magma ocean cumulates to produce the green glasses. This provides evidence for the magma overturn hypothesis, as well as evidence that the lunar magma ocean may not have been whole moon. Chapter 3 uses phenocryst petrology, Os-isotopes, major and trace element geochemistry and petrography to argue for the formation of primitive magnesian andesites of Mt. Shasta and Mt. Lassen as primary mantle melts. Recent proposals that primitive magnesian andesites form by mixing dacites with subvolcanic peridotite are disproven. Samples of these lavas from newly discovered localities provide clear evidence for a mantle origin for these melts. Understanding the primitive melts present in the Cascade volcanoes will yield greater insight into the mantle processes involved in the plumbing of the sub-arc mantle. Chapter 4 develops a ternary regular solution model for Au-Pd-Fe alloys and uses this with Fe-exchange experiments to model the dependence of alloy composition on the oxygen fugacity. Au-Pd alloy capsules are essential to hydrous phase equilibrium studies at high-pressure and high-temperature, and the use of this model allows for the quantification of the oxygen fugacity of these experiments without compromising sample volume.
by Jay Arthur Barr.
Ph.D.

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Berlo, Kim. "Time scales of magma evolution at Mount St. Helens." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432346.

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Harford, Chloe Linden. "The volcanic evolution of Montserrat." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343316.

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Braithwaite, J. W. H. "Heavy element partitioning and the evolution of the magma ocean." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10044908/.

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Density contrasts between liquids and crystals are vital to the understanding of how the mantle evolved from its molten beginnings to its current day state. As we approach the pressures of the core-mantle boundary, liquid densities tend to those of isochemical crystals, but do not exceed them. Consequently an understanding of how heavy elements, such as iron and calcium, partition between crystal and liquid phases is vital to determining the densities. The methodology is based upon using molecular dynamics driven by density functional theory (DFT). In the first instance the technique of thermodynamic integrations is used to compute free energy differences between iron-bearing and iron-free systems. From this we can determine the effects of pressure, temperature and iron concentration on the partitioning. In all of our results we find that the liquid phase is strongly favoured by iron. For ferropericlase, (Mg,Fe)O, good agreement is seen with cited work at low pressures. The partitioning method is also applied to bridgmanite, (Mg,Fe)SiO3. Here the values determined for the partitioning favour the liquid more strongly than that of main experimental comparison. We attribute this to the presence of Al3+ and ferric (Fe3+) iron. We show evidence for the mantle crystallising from the centre outwards and the possible existence of long lasting melts at the base of the mantle.

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Redner, Ellen R. "Magma Mixing and Evolution at Minna Bluff, Antarctica Revealed by Amphibole and Clinopyroxene Analyses." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1474028057097791.

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Armshaw, Derek. "Garnet- and clinopyroxene-liquid equilibria at high pressure : an experimental study in part of the system CaO-MgO-FeO-Al₂O₃-SiO₂ with relevance to garnet-lherzolites." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/11387.

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Murphy, Michael D. "Magmatic evolution at volcan Sollipulli, southern Andes of Chile." Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/7e0aef3b-940d-4e3b-bfc7-f5b483708044.

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Volcan Sollipulli is a Quaternary stratovolcano situated at 38'50'S in the Southern Volcanic Zone of the Andes of Chile, about 25 km east of the volcanic front. The volcano is capped by a large (25 km2 approx. ) ice-filled caldera. Sollipulli is unusual in this region of predominantly basic to intermediate magmatism in that it has erupted a wide range of magmas from high-MgO (9%) basalt to rhyolite (74% Si02). The last major eruption, the Alpehue eruption, occurred at about 2,900 B. P, ejecting about 4.7 km3 (D. R. E) of homogeneous high-Si dacite pumice, forming an extensive plinian airfall deposit and ignimbrite. The caldera predates the Alpehue eruption and is believed to have formed by passive subsidence combined with erosion rather than by catastrophic collapse. Withdrawal of magma from beneath the centre of the structure and effusive eruption induced subsidence. Magma mixing, fractional crystallisation and crustal assimilation are important evolutionary mechanisms. Some mixed dacite lavas contain primitive basaltic magmatic inclusions with diktytaxitic textures indicative of rapid quenching. Strongly resorbed, reverse zoned sodic plagioclase of dacitic origin occurs in basic inclusions and high-Mg olivine occurs in dacites. Other sequences appeart o have evolved predominantly by fractional crystallisation with some crustal assimilation. The amount of crustal assimilation increasesw ith decreasinga gei n somec ases. Older Sollipulli basic magmash ave evolved as small batchesp redominantlya t moderatet o high pressurein the mid-lower crust whereas younger basic magmas have experienced protracted upper crustal histories in a large magma chamber, fractionating and assimilating crust to produce abundant high-Si dacite. Sollipulli magmas have an anhydrous mineralogy except for the occurrence of very minor amphibolei n somem ixed rocks. Magma temperaturesra ngef rom about 118 0'C in basalts to about 900'C in dacites. The most primitive samples represent hot and relatively water-poor (<1-2% H20) high-Al basaltic magmas. Crystal-rich andesitesa nd dacites record lower temperaturesth an crystal-poore quivalents. The cooler porphyritic magmas appear to have assimilated more crust than the hotter crystal-poor magmas. Most magmas have evolved at oxygen fugacities close to the NNO buffer curve. Large volcanic front centres in the region erupt magmas with lower incompatible elementa bundancea nd higher Ba/Nb than magmase rupteda t minor monogeneticc entresa, nd at stratovolcanoesto the easto f the front, which have incompatiblee lements ignatures transitional towards back-arc alkaline magmas (e. g. high Nb, Ce/Y). Older Sollipulli magmas also have high Ce/Y and Nb similar to magmas at some monogenetic centres but have lower Ti and Y. Younger Sollipulli magmas have even lower Ti and Y. Sollipulli basic magmasa re also characterisedb y higher Mg/Ni than all regional magmas. The simplest explanation is that the high Nb, Ce/Y magmas have assimilated enriched mantle lithosphere. The Ti, Y, Mg/Ni systematics suggest that the Sollipulli magmasa re generated by higher degrees of melting of a similar MORB-source-type mantle than the regional magmas. In the case of the younger Sollipulli magmas, generation from mantle which was slightly depleted during the earlier phase is also possible but the older magmas show no evidence in their spinel compositions for derivation from refractory mantle.

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Salvador, Arnaud. "Evolution primitive et habitabilité des planètes rocheuses." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS439/document.

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Les planètes rocheuses achèvent leur formation dans des processus collisionnels très énergétiques.L'énergie libérée lors des impacts majeurs a vraisemblablement fondu la surface des planètes, formant ainsi un océan de roches en fusion. Le refroidissement et la solidification de cet « océan de magma » conditionnent la différentiation chimique du manteau et la distribution des éléments volatils entre les différents réservoirs de la planète. C'est lors de cette phase évolutive, commune aux planètes rocheuses, que l'atmosphère est formée par dégazage des volatils et que les conditions initiales de l'évolution future des planètes se mettent en place. C'est ainsi une phase évolutive de première importance pour comprendre l'apparition des océans d'eau primitifs, le démarrage de la convection thermique du manteau et l'actuelle diversité des planètes telluriques.Un modèle numérique couplant l'évolution thermique de l'océan de magma en interaction avec l'atmosphère a été utilisé pour étudier le refroidissement de la planète et les conditions de surface résultantes. Nous avons investigué l'influence du contenu initial en volatil combiné avec la distance orbitale de la planète sur la formation des premiers océans d'eau à la fin du refroidissement, pour des atmosphères avec et sans nuages. Cette approche a ensuite été étendue aux planètes rocheuses extra-solaires orbitant des étoiles froides.Le contenu relatif en H2O et CO2 de l'atmosphère peut empêcher la formation d'océans, menant à des planètes ayant une surface solide sans océans d'eau. Des lois d'échelle prédisent la formation d'océans en fonction du contenu initial en volatil. Une épaisse couche nuageuse diminue la température de surface et maintient des conditions clémentes plus proche de l'étoile rendant ainsi possible la formation d'océan sur Vénus. Ces conditions de surface tempérées pourraient alors être favorable à l'émergence de la vie et suggèrent qu'en fonction de la couverture nuageuse, la Terre et Vénus pourraient être dans un état relativement similaire à la fin de la phase océan de magma, contrairement à ce qui est généralement admis.Pour les étoiles froides, la formation d'océans d'eau n'est possible qu'à des flux stellaires plus faibles que dans notre système solaire, correspondant à des distances étoile-planète relativement plus importantes.L'effet refroidissant des nuages est atténué pour les étoiles froides autour desquelles la bordure intérieure de la zone d'habitabilité tend à être indépendante de la couverture nuageuse
At the end of the accretion phase, rocky planets grow through high energetic impact processes. Combined with other heat sources, they most likely melt the surface of the planets, forming an ocean of molten rocks. The cooling and solidification of this early so-called magma ocean strongly influences the earliest compositional differentiation and volatile distribution of the planet. Indeed, this common early evolution stage of rocky planets witnesses the degassing of the atmosphere and sets the initial conditions for the long-term evolution of the planets. It is thus of major importance in understanding the formation of the primitive water ocean, the onset of thermally driven mantle convection and the diversity of observed terrestrial planets.Using a coupled magma ocean-atmosphere thermal evolution model, we investigated the cooling of the planet and the surface conditions reached at the end of this early stage. We studied how the initial volatile content and the distance from the star influence the formation of a water ocean at the end of the cooling for both cloud-free and cloudy atmospheres. We extended this approach to planets orbiting colder stars than the Sun.The relative amount of H2O and CO2 in the atmosphere can preclude water ocean formation, leading to solid surface planets without water ocean. Scaling laws are derived to predict the formation of a water ocean as a function of the initial volatile content.The presence of a thick cloud cover extends clement surface conditions close to the star and allows for water ocean formation on early Venus. Such temperate conditions might be suitable for the emergence of life and suggest that, depending on the cloud cover, the Earth and Venus might not be as different as previously thought at the end of the magma ocean stage.For stars colder than the Sun, water ocean formation is shifted to farther star distances. The cooling effect of clouds becomes less efficient for cold stars whose inner edge of the temperate zone tends to be independent of the cloud cover

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Moussallam, Yves. "Magma ascent and redox evolution at Erebus volcano : observational and experimental constraints." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648408.

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Sun, Yang. "Magma Evolution of the Cerro Bayo Laccolith in the Chachahuén Volcanic Complex, Argentina." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360467.

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The Chachahuén volcanic complex, with the Cerro Bayo laccolith as one of the largest intrusions, is part of back-arc Payenia volcanic province in western central Argentina. Laccoliths show potential for generating oil in sedimentary basins and producing ore deposits. It is crucial to put more effort into understanding the magma plumbing system beneath the Chachahuén volcanic complex, which the Cerro Bayo laccolith is part of. Thus this project present the first thermobarometric modelling for the Cerro Bayo laccolith and the Chachahuén volcanic complex. Several thermometers and barometers were applied to plagioclase, amphibole and clinopyroxene to understand magma evolution in the underlying plumbing system. The dacitic to rhyodacitic laccolith rocks from Cerro Bayo have porphyric textures with plagioclase in the form of both clots (glomerocrysts) and single crystals, amphibole and clinopyroxene as main phenocrysts, while enclaves are more mafic in composition and have equigranular textures. Plagioclase in the sample varies from andesine to labradorite with a composition of An22-An68, while the clinopyroxene can be classified into diopside to augite with cores (Mg#=76-84) and rims (Mg#62-72). Amphibole, varies from pargasite, ferropargasite to magesiohastingsite and hastingsite, which can be grouped into three groups according to the Mg#: low Mg# amphibole (Mg# = 40-51), medium Mg# amphibole (Mg# = 52-61) and high Mg# amphibole (Mg# = 62-78). Besides, most of the Fe-Ti oxides in the samples are titanomagnetite with Usp mol.% in the range of 0.04-0.54. Results from clinopyroxene-liquid thermobarometers suggest a crystallization depth of 44 to 51 km for clinopyroxene cores and a crystallization depth of 19 to 31 km for rims, of which the derived crystallization temperatures are in the range of 1144 to 1170 °C and 973 to 1002 °C respectively. On the other hand, different thermobarometers of amphibole give consistent results of crystallization temperatures and depths. According to the amphibole-liquid thermometer, low Mg# (Mg#= 40-51) amphiboles have the lowest crystallization temperature in the range of 898 to 931°C, while medium Mg# (Mg#=52-61) amphiboles have higher crystallization temperatures in the range of 951 to 972°C and high Mg# (Mg# = 62-78) amphiboles have highest crystallization temperatures between 991 and 1013°C. The depth translated from pressure derived from amphibole-liquid barometers give a shallower crystallization depth range from 19 to 30 km for low Mg# amphiboles, a deeper crystallization depth in the range of 22 to 39 km for high Mg# amphiboles and deepest crystallization depth range of 27 to 41 km for medium Mg# amphiboles. Moreover, a depth from 2 to 20 km could be gained from the plagioclase-liquid thermobarometry which crystallized at 883 to 910°C. It is worth to point out that crystallization depth of clinopyroxene cores is deeper than the Moho in the Chachahuén area, while crystallization depth and temperatures of clinopyroxene rims are consistent with those of high Mg# amphiboles. Consistent temperatures and depths are also found for crystallization of plagioclase and low Mg# amphiboles which intergrow with each other. Thus, a multi-level magma plumbing system began from below the Moho, with a mushy zone in the upper crust, could be suggested to exist beneath the Cerro Bayo laccolith. Evidence from both petrology and geochemistry also indicate fractional crystallization as well as processes of magma mixing and recharge during magma evolution.
Chachahuén火山综合体，包含其最大的侵入体Cerro Bayo岩盘，是位于阿根廷中西部Payenia弧后火山区的一部分。前人研究多着重于岩石学、地球化学和地层学方面，因而针对下伏岩浆涌升系统的研究在该地区极具前瞻性，需要投入更多工作。本文首次尝试对Chachahuén火山复合体应用温压计进行研究，针对斜长石、角闪石和单斜辉石应用了不同的温度计和压力计，以揭示下伏于Cerro Bayo岩盘的岩浆涌升系统中的岩浆演化。来自Chachahuén火山复合体Cerro Bayo岩盘的英安质-流纹英安质火成岩具有板状-似斑状结构，其斑晶主要为单晶或聚合物形式存在的斜长石、角闪石及单斜辉石。此外，岩盘中还发现具等粒结构的酸性捕虏体的存在。样品中斜长石（An=22-68）主要成分为中长石至拉长石.单斜辉石主要为透辉石和普通辉石，常发育高镁值核部（Mg#=76-84）和低镁值环带（Mg#62-72）。角闪石主要为韭闪石、铁韭闪石、镁绿钙闪石和绿钙闪石，可根据镁值进一步划分为三个组：低镁值组（Mg# = 40-51），低镁值组（Mg# = 52-61）和高镁值组（Mg# = 62-71）。此外，样品中的钛铁氧化物重要为钛磁铁矿（Usp%=0.04-0.54）。单斜辉石-熔体温压计的结果表明单斜辉石的核部和环带的结晶温度和深度有所差异：核部具有较高的结晶温度（1144-1170 °C）和较深的结晶深度（44-50km），而环带具有较低的结晶温度（973-1002 °C）和较浅的结晶深度（18-31 km）。与角闪石相关的不同温压计给出了类似的结晶温度和压力，其中存在的微小差异均在误差范围内。因此本文将角闪石-熔体温压计的结果作为最终结果，其显示低镁值角闪石具有较低结晶温度（898-931°C），中镁值角闪石具较高结晶温度（951-972°C），而髙镁值角闪石具最高结晶温度（991-1013°C）。角闪石的结晶深度特征有所不同：低镁值角闪石的结晶深度最浅（19-30km），髙镁值角闪石的结晶深度较深（22-39 km），反而中镁值角闪石结晶深度最深（27-41 km）。斜长石-熔体温压计给出的斜长石结晶温度和深度分别为883-910°C及1-20km。值得一提的是单斜辉石核部的结晶深度位于研究区莫霍面之下。同时，单斜辉石的环带与髙镁值角闪石具有相似的结晶温度和深度，而斜长石及共生的低镁值角闪石具有相似的结晶温度。因此可以推测，Cerro Bayo岩盘之下，发育一个自莫霍面之下开始的多层岩浆上涌系统。而岩石学和地球化学的证据还表明在岩浆发育过程中岩浆分化结晶和岩浆重注和混合作用并存。
En lakkolit är en grund magmaficka och en vanligt förekommande del av en vulkan, vilken kan bilda en länk mellan djupa magmatiska aktiviteter och vulkanutbrott. Forskning om kompositionen och bildandet av grunda magmafickor kan hjälpa till att öka förståelsen om geologiska faror och naturresurser. Vid Cerro Bayo exponeras en grund magmakammare vilken utgör en del av Chachahuén vulkankomplexet i Argentina. Det här projektet fokuserar på det magmatiska lagringssystemet och magmautvecklingen vid Cerro Bayo. Magmasammansättningen och magmakammarens förhållanden såsom tryck, temperatur och vattenhalt samt vattensystemets struktur är viktiga faktorer som styr magmatiska processer. För att förstå magmautvecklingen under Cerro Bayo inleddes projektet med en kompositionsanalys av bergprover och mineral. Därefter genomfördes termobarometrisk modellering för att bestämma temperatur- och tryckförhållandena för kristalliseringen av mineraler i det magmatiska systemet. Resultaten av modelleringen tyder på att ett magmatiskt rörsystem av flera nivåer existerar under Cerro Bayo lakkoliten. Det djupaste magmamagasinet ligger på 44-50 km och når upp till 22-41 km i nedre jordskorpan, medan de grunda reservoarerna av magma ligger på ett djup av 2-20 km i övre jordskorpan som slutligen når den grunda magmafickan. Vidare indikerar analysen av mineralstruktur och mineralkemi processer av fraktionerad kristallisering samt påfyllning och blandning av magma under magmautvecklingen. Magman genomgick fraktionerad kristallisering under rörelser uppåt från de djupaste magmakammarna. Magmans temperatur varierar från högre än 1100 ° C till ~ 900 ° C. Ansamlingar av magma fortsatte att fylla på magmamagasin i nedre och övre jordskorpan. Blandning av magma inträffade när en ansamling varmare magma rörde sig från nedre till övre jordskorpreservoarer och påverkade såväl migrering av magma som placeringen av Cerro Bayo lakkoliten

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Forni, Francesca <1979&gt. "Petrology and geochemistry of Lipari Island (Aeolian archipelago): constraints on magma genesis and evolution." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3785/.

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A full set of geochemical and Sr, Nd and Pb isotope data both on bulk-rock and mineral samples is provided for volcanic rocks representative of the whole stratigraphic succession of Lipari Island in the Aeolian archipelago. These data, together with petrographic observations and melt/fluid inclusion investigations from the literature, give outlines on the petrogenesis and evolution of magmas through the magmatic and eruptive history of Lipari. This is the result of nine successive Eruptive Epochs developing between 271 ka and historical times, as derived from recentmost volcanological and stratigraphic studies, combined with available radiometric ages and correlation of tephra layers and marine terrace deposits. These Eruptive Epochs are characterized by distinctive vents partly overlapping in space and time, mostly under control of the main regional tectonic trends (NNW-SSE, N-S and minor E-W). A large variety of lava flows, scoriaceous deposits, lava domes, coulees and pyroclastics are emplaced, ranging in composition through time from calcalkaline (CA) and high-K (HKCA) basaltic andesites to rhyolites. CA and HKCA basaltic andesitic to dacitic magmas were erupted between 271 and 81 ka (Eruptive Epochs 1-6) from volcanic edifices located along the western coast of the island (and subordinately the eastern Monterosa) and the M.Chirica and M.S.Angelo stratocones. These mafic to intermediate magmas mainly evolved through AFC and RAFC processes, involving fractionation of mafic phases, assimilation of wall rocks and mixing with newly injected mafic magmas. Following a 40 ka-long period of volcanic quiescence, the rhyolitic magmas were lately erupted from eruptive vents located in the southern and north-eastern sectors of Lipari between 40 ka and historical times (Eruptive Epochs 7-9). They are suggested to derive from the previous mafic to intermediate melts through AFC processes. During the early phases of rhyolitic magmatism (Eruptive Epochs 7-8), enclaves-rich rocks and banded pumices, ranging in composition from HKCA dacites to low-SiO2 rhyolites were erupted, representing the products of magma mixing between fresh mafic magmas and the fractionated rhyolitic melts. The interaction of mantle-derived magmas with the crust represents an essential process during the whole magmatic hystory of Lipari, and is responsible for the wide range of observed geochemical and isotopic variations. The crustal contribution was particularly important during the intermediate phases of activity of Lipari when the cordierite-bearing lavas were erupted from the M. S.Angelo volcano (Eruptive Epoch 5, 105 ka). These lavas are interpreted as the result of mixing and subsequent hybridization of mantle-derived magmas, akin to the ones characterizing the older phases of activity of Lipari (Eruptive Epochs 1-4), and crustal anatectic melts derived from dehydration-melting reactions of metapelites in the lower crust. A comparison between the adjacent islands of Lipari and Vulcano outlines that their mafic to intermediate magmas seem to be genetically connected and derive from a similar mantle source affected by different degrees of partial melting (and variable extent of crustal assimilation) producing either the CA magmas of Lipari (higher degrees) or the HKCA to SHO magmas of Vulcano (lower degrees). On a regional scale, the most primitive rocks (SiO2<56%, MgO>3.5%) of Lipari, Vulcano, Salina and Filicudi are suggested to derive from a similar MORB-like source, variably metasomatized by aqueous fluids coming from the slab and subordinately by the additions of sediments.

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Lebrun, Thomas. "Evolution thermique d'un océan de magma primitif en interaction avec l'atmosphère : conditions pour la condensation d'un océan d'eau." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00931698.

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La recherche de nouvelles formes de vie est une quête passionnante mais quidemande avant tout de comprendre l'origine de l'apparition d'une forme de vie.La seule planète qui abrite la vie à notre connaissance est la Terre. Comprendrepourquoi les autres planètes de notre système solaire n'en abrite pas ou plus estune étude nécessaire pour pouvoir mieux cibler nos cherches de nouvelles vies dansles autres systèmes stellaires. L'objectif de cette thèse est d'apporter des premierséléments de réponse à cette question. Nous nous sommes principalement concentréssur la comparaison d'évolution thermique entre Mars, la Terre et Vénus vers lafin de leur accrétion lors du refroidissement de leur océan de magma. L'évolutionthermique d'océans de magma produits par collision avec des impacteurs géantslors de l'accrétion est supposée dépendre de la composition et de la structure del'atmosphère à travers l'effet de serre du CO2 et H2O relâché par le magma durantsa cristallisation. Afin de contraindre les différentes échelles de temps de refroidissementdu système, nous avons développé un modèle 1-D de convection paramétréd'un océan de magma couplé avec un modèle atmosphérique 1-D radiatif-convectif.Nous avons conduit une étude paramétrique et décris l'influence de plusieurs variablestelles que le contenu initial en volatils, la profondeur initiale de l'océan demagma ou encore la distance planète-soleil. Nos résultats suggèrent que la présenced'une atmosphère de vapeur retarde la fin de la phase d'océan de magma d'environ1 Ma. De plus, nous observons également que la vapeur d'eau condense en un océanaprès 0.1, 1.5 et 10 Ma respectivement pour Mars, la Terre et Vénus. Ce tempsserait virtuellement infini pour une planète de la taille de la Terre située à moins de0.66 ua du soleil. Au regard de ces résultats, nous remarquons que pour la Terre etMars, les échelles de temps de formation d'un océan d'eau sont plus courtes que lagamme de temps entre chaque impacts majeurs. Ceci impliquerait que des océansd'eau successifs peuvent s'être développés durant l'accrétion. En revanche, Vénus,du fait de sa grande proximité avec le seuil de distance au soleil (0.66 ua), pourraitavoir maintenu sa phase d'océan de magma plus longtemps durant l'accrétion.Par la suite, la prise en compte de l'échappement hydrodynamique nous a permisde constater que ce phénomène a très peu d'incidence sur le réservoir global d'eaud'une planète durant la phase d'océan de magma. Cependant, on observe qu'aprèsla condensation de la vapeur d'eau, l'échappement devient de plus en plus efficaceet le réservoir d'eau fini par être totalement évaporé peu de temps avant la fin de lasolidification du manteau. Enfin, nous avons commencé à étudier l'influence d'autresgros impacts durant le refroidissement de l'océan de magma. Les premiers résultatsmontrent que dans le cas de Mars et la Terre, la durée de leur phase d'océan demagma est plus courte que la gamme de temps entre chaque impact majeur. Il en résulte que ces planètes ont dû connaitre une alternance entre phase d'océan demagma et phase d'océan d'eau. Ce phénomène n'a en revanche pas dû avoir lieusur Vénus. En effet, la durée de sa phase d'océan de magma est plus longue que lagamme de temps entre chaque impact majeur. C'est pourquoi, la phase d'océan demagma sur Vénus a dû se prolonger durant toute la phase d'impacts et qu'aucunocéan d'eau n'a pu se former avant la fin de cette période.

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14

Saalfeld, Megan A. "Petrology of the 1877 eruption of Cotopaxi Volcano, Ecuador: Insight on magma evolution and storage." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1515422098880506.

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15

Rivard, Benoit. "Petrochemistry of a layered Archean magma chamber and its relation to models of basalt evolution." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66046.

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16

Pugliese, Stefano. "Multiple magma mingling, enclave typology and textural evolution in the Ross of Mull granite, Scotland." Thesis, Kingston University, 1999. http://eprints.kingston.ac.uk/20635/.

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The Ross of Mull Igneous Complex consists of a suite of syn-post tectonic lamprophyric-dioritic-microdioritic-monzogranitic calc-alkaline bodies emplaced hito Moinian metasediments (P=2-3 kbar) throughout the closing stages of the Caledonian orogeny (414±3 Ma; Halliday et al., 1979). The pluton occupies an area approximately 140 km[sup]2, of which only half is exposed on the mainland - the rest is submerged. Microdioritic and dioritic bodies are confined to the core of the pluton and occupy topographic lows, while granites occupy the highs. The distribution of these plutonic rocks is interpreted as a compositionally zoned (reversed) magma chamber. Prior to and throughout the main phase of monzogranite emplacement, a series of basaltic (alkalic) magma pulses intruded the monzogranitic magma chamber, inducing mechanical mixing, homogenisation and the production of a hybrid porphyritic monzogranite. Binary mixing equations allow the proportions of granitic magma involved in the mixing event to be estimated, which vary between 66-80%. Continued injection of basaltic magma into the evolving, crystal-ladden, porphyritic monzogranitic magma chamber resulted in the fragmentation of the basaltic magma and the formation (preservation) of megacrystic, microdioritic enclaves. On the basis of alkali feldspar crystal growth rates in granitic magmas, as well as thermodynamical considerations (e.g. Furman & Spera, 1985), the time elapsed between the formation of the porphyritic monzogranite and the injection of additional basaltic magma pulses was approximately 15000 years. Based on detailed field mapping and petrographic analysis, microdioritic enclaves can be subdivided into four texturally distinct populations, depending on their megacrystic mineralogy. The mineralogy and textures of the enclaves reflect and record the point at which the basaltic magma intruded the crystallising porphyritic monzogranitic magma chamber. Generally, highly megacrystic microdiorites are interpreted as having been intruded relatively early in the crystallisation history of the porphyritic monzogranite. Microdioritic enclaves with fewer megacrysts are likely to have been emplaced late in the crystallisation of the granite, when the rheological differences between the two magmas would have inhibited mingling. In exceptional circumstances, microdioritic bodies and enclaves become veined by thin (c. 5 mm wide) leucocratic (monzonitic) veins composed of plagioclase + alkali feldspar ± quartz. Typically, these veins occupy 5-30% volume of the microdiorite. Field and mineralogical evidence cannot equivocally explain the formation of the monzonitic veins. Partial melting experiments on megacryst-free microdioritic enclaves at crustal pressures and temperatures (i.e. 750-950 °C, 50 MPa), have therefore been carried out in order to shed light on the origin of the veining phenomena. The composition of the melt generated during these experiments requires high (950 °C) temperatures and is less sodic but richer in quartz than that of the leucocratic veins. Integrated field, mineral chemistry and geochemical data suggests that mechanical mixing of basaltic and porphyritic monzogranite magma (at depth or in a conduit) produced a heterogeneous mixture which was injected into a porphyritic monzogranitic magma chamber. The higher liquidus of the basaltic magma coupled with the input of additional heat from new basaltic magma pulses induced fluid-present partial melting of the more fusible components in the mixture (i.e. the granitic end-member). Where the mixture was almost crystalline prior to incorporation into the porphyritic monzogranite, re-heating of the mixture caused recrystallisation of the microdioritic matrix, partial melting of the granitic material and thermal expansion leading to the formation of a feldspar-rich, pseudo-polygonal monzonitic vein network (e.g. pink veined microdiorites). However, in the case where the mixture was still ,largely molten prior to incorporation into the porphyritic monzogranite, fluid-present partial melting of the granitic material in the mixture caused the formation of feldspar + quartz-rich leucocratic veins without recrystallisation of the microdiorite matrix (e.g. white veined microdiorites). As melting of the granitic magma ensued, monzonitic melt exfiltrated through the partially molten microdiorite matrix via porous flow and deformation enhanced melt segregation mechanisms. The topology of the vein network will have a fundamental bearing on the efficacy of chemical homogenisation within the microdiorites, as well as controlling the rate of material transport (advection) within the veins. Leucocratic veins are clearly linked in three dimensions and in order to quantify the pore structure of the veins, a veined microdioritic enclave was collected for serial sectioning. Image analysis software and 3D modelling packages were then used to reconstruct the vein network in 3D. The results show that the vein network posseses a high effective porosity (17%), as well as a complex bifurcating and branching network. Based on the 3D topology, the specific permeability (k) of the vein network has been estimated and ranges from 8x10[sup]-7 to 1x10[sup]-12 m[sup]2. Based on these permeabilities and estimates of granitic melt viscosities (10[sup]4 to 10[sup]8 Pas), Darcian flow velocities range from 10[sup]-6 to 3 m[sup]2 yr[sup]-1. The extensive connectivity of the channel network in the veined microdiorites suggests that element mobility during active flow would have been extensive.

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Watanabe, Shizuko. "The Evolution of a Chemically Zoned Magma Chamber: the 1707 Eruption of Fuji Volcano, Japan." Oxford, Ohio : Miami University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1070588662.

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Thesis (M.S.)--Miami University, Dept. of Geology, 2003.
Title from first page of PDF document. Document formatted into pages; contains viii, 105 p. : ill. Includes bibliographical references (p. 83-91).

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18

Hartsock, Tanner. "Magma evolution, P-T conditions and volatile degassing of a steady-state volcano: Yasur, Vanuatu." Thesis, University of Iowa, 2019. https://ir.uiowa.edu/etd/6757.

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Yasur is an active scoria cone volcano in the Siwi Caldera on the island of Tanna, Vanuatu, in the South Pacific. This volcano has been erupting continuously for the last 800 years and is the latest manifestation of episodic volcanic activity in this area dating back to the late Pliocene. Yasur eruptions consist of intermittent Strombolian-style explosions of pyroclastic debris with emissions of volatiles such as SO₂, HCl and HF. Other than CO2 and H2O, the most abundant gas emitted from Yasur is sulfur, and plume monitoring has confirmed the volcano as one of the largest point sources of sulfur on the planet with an average flux of 600-1400 tons/day. Fluorine poses a chronic environmental health risk on Tanna, so understanding long-term exposure rates as well as periodic increases in volcanic intensity will help to better quantify its risk. In this study we gauge compositional variation of magma using fresh pyroclastic bombs collected over a 3-month period from August to November, 2016. Our results suggest long-term broad compositional stability in both the whole-rock and groundmass glass and minerals. Our results show slight variation in volatile phases in both olivine-hosted melt inclusions and groundmass glass over an intensively sampled 3-month period, which suggests that the plumbing beneath Yasur harbors an open-system degassing environment. Volcanic eruptions are usually driven by magma mixing, however, our results show no compositional variation in phenocrysts. We show that Yasur is an excellent example of an inefficiently degassed volcano, and that volcanic activity is controlled by volatile flux. We also use cotectic compositional data to calculate pressure and temperature conditions within the magma chamber and assess fluxes of volatiles from the magma using melt inclusion analyses for S and Cl. Our study places new bounds on the vertical extent of the magma chamber and suggests differentiation from a basaltic trachyandesite at depths of up to 12 km.

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19

Hayes, Stephen John. "Magmatic evolution of the Shira Volcanics, Mt Kilimanjaro, Tanzania." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15963/1/Stephen_Hayes_Thesis.pdf.

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Mt Kilimanjaro, Africa's highest mountain (5895m), is a large, young (<1.6Ma) stratovolcano at the southern end of the East African Rift, in northern Tanzania. Consisting of three distinct volcanic centres, Shira, Mawenzi and Kibo, Shira contains the highest proportion of mafic rocks. Shira samples are strongly silica under-saturated rocks, ranging from picro-basalt, to nephelinite and hawaiite (Mg numbers (Mg #) ranging from 77.2-35.5). Phenocrysts constitute up to 55% of some samples, and include aluminous augite (often containing abundant fluid and/or melt inclusions), olivine (Fo92-Fo49), plagioclase (An75-An42), nepheline (Ne77-Ne68), magnesiochromite and ulvöspinel. Groups identified on the basis of phenocryst assemblages and textures correlate with location. East Shira Hill samples contain olivine and clinopyroxene phenocrysts + microphenocrysts of plagioclase (Group 1), or plagioclase and clinopyroxene phenocrysts + microphenocrysts of olivine (Group 2). Samples with high Mg #'s contain abundant cumulate clinopyroxene and olivine (Fo92-Fo85). Group 3 samples (Shira Ridge) contain nepheline phenocrysts and Group 4 samples (Platzkegel) have distinct intergranular textures. Chondrite normalised REE patterns are steep, with light REE-enrichment up to 400x chondrite. Spider diagrams, normalised to OIB for primitive Shira samples have strong K depletions and Pb enrichments. The source of the Shira volcanic rocks is most likely an amphibole-bearing spinel lherzolite, in which amphibole remains residual. Similarities in spider diagram patterns and trace element ratios suggest a source similar to average OIB. The Shira volcanic centre is a polygenetic volcano, in which multiple small volume, low degree (4-10%) partial melts from a metasomatised subcontinental lithospheric mantle follow pre-existing structural weaknesses, before ponding in the lithosphere. Evolution of these small volume melts is dominated by shallow fractional crystallisation of clinopyroxene, olivine±spinel, with plagioclase also fractionating from Group 4 (Platzkegel) samples. A magma mixing origin is suggested for some samples and supported by complex zonation patterns in major and trace element chemistry of clinopyroxene phenocrysts as well as linear mixing arrays. The Shira volcanic centre has since ceased activity, and collapsed to form the present day Shira Ridge and caldera before being overlain by various Kibo and parasitic lavas to the east and northwest of the Shira region.

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20

Hayes, Stephen John. "Magmatic evolution of the Shira Volcanics, Mt Kilimanjaro, Tanzania." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15963/.

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Mt Kilimanjaro, Africa's highest mountain (5895m), is a large, young (<1.6Ma) stratovolcano at the southern end of the East African Rift, in northern Tanzania. Consisting of three distinct volcanic centres, Shira, Mawenzi and Kibo, Shira contains the highest proportion of mafic rocks. Shira samples are strongly silica under-saturated rocks, ranging from picro-basalt, to nephelinite and hawaiite (Mg numbers (Mg #) ranging from 77.2-35.5). Phenocrysts constitute up to 55% of some samples, and include aluminous augite (often containing abundant fluid and/or melt inclusions), olivine (Fo92-Fo49), plagioclase (An75-An42), nepheline (Ne77-Ne68), magnesiochromite and ulvöspinel. Groups identified on the basis of phenocryst assemblages and textures correlate with location. East Shira Hill samples contain olivine and clinopyroxene phenocrysts + microphenocrysts of plagioclase (Group 1), or plagioclase and clinopyroxene phenocrysts + microphenocrysts of olivine (Group 2). Samples with high Mg #'s contain abundant cumulate clinopyroxene and olivine (Fo92-Fo85). Group 3 samples (Shira Ridge) contain nepheline phenocrysts and Group 4 samples (Platzkegel) have distinct intergranular textures. Chondrite normalised REE patterns are steep, with light REE-enrichment up to 400x chondrite. Spider diagrams, normalised to OIB for primitive Shira samples have strong K depletions and Pb enrichments. The source of the Shira volcanic rocks is most likely an amphibole-bearing spinel lherzolite, in which amphibole remains residual. Similarities in spider diagram patterns and trace element ratios suggest a source similar to average OIB. The Shira volcanic centre is a polygenetic volcano, in which multiple small volume, low degree (4-10%) partial melts from a metasomatised subcontinental lithospheric mantle follow pre-existing structural weaknesses, before ponding in the lithosphere. Evolution of these small volume melts is dominated by shallow fractional crystallisation of clinopyroxene, olivine±spinel, with plagioclase also fractionating from Group 4 (Platzkegel) samples. A magma mixing origin is suggested for some samples and supported by complex zonation patterns in major and trace element chemistry of clinopyroxene phenocrysts as well as linear mixing arrays. The Shira volcanic centre has since ceased activity, and collapsed to form the present day Shira Ridge and caldera before being overlain by various Kibo and parasitic lavas to the east and northwest of the Shira region.

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21

Li, Yuyu M. S. "Petrologic Insights into Basaltic Magma Genesis beneath East Antarctica." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1593363487482443.

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22

Esposito, Rosario. "Studies of volatile evolution in magmatic systems using melt inclusions." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28287.

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Understanding volatile evolution associated with active volcanic magmatic systems is of paramount importance because volatiles control and determine the magnitude of an eruption owing to the large change in molar volume that volatile species show depending on their physical state (volatiles dissolved in silicate melts vs. volatiles exsolved as vapor). For active volcanic systems studying the volatile evolution can help to assess the potential hazard associated to a certain locality. Also, volatile evolution in magmatic system controls the formation of certain ore deposits. Despite the importance of understanding volatile evolution of magmatic systems, concentrations of volatiles of evolving magmas are not easily available especially for magmas originated in the deep crust. Fortunately, sample of melts can be entrapped as melt inclusion (MI) into growing igneous minerals in crystalizing magma chamber. After the entrapment, the crystal works as an insulating capsule from the external magmatic environment. Researchers have started to use MI because they provide some advantages in respect to the classical whole rock approach to petrological studies. One of the most important advantages is that MI often represent sample of a deep and non-degassed melt (glass) available at Earth's surface. In fact, with the exception of deep ocean basalts, igneous whole rocks found at the Earth's surface are degassed magmas. This dissertation is a compilation of four publications produced during six years of research and is addressed to give a contribution in understanding the volatile evolution in magmatic systems and also to improve the present understanding of information that can be obtained using the melt inclusions technique. In the first chapter, I present an alternative interpretation of H₂O-CO₂ trends obtained from MI. In this study, we demonstrate that these trends can be due to post entrapment crystallization on the wall of the MI and not to magma ascent. This alternative view is more realistic especially for cases where in the same phenocrysts MI show strongly different CO₂ concentrations. In the second chapter, I present a study to test for the MI reliability in recording volatile concentrations. We used the approach of the melt inclusion assemblage (MIA) that consists of analyzing groups of MI presumably entrapped at the same time and, thus, at same chemical and physical conditions. The results show that most of the MIA studied show consistent volatile concentrations corroborating the reliability of the MI technique. CO₂ shows the highest degrees of variability and we have assessed this behavior mostly to C-contamination in the surface of the sample. The third chapter is a study case (the Solchiaro eruption in Southern Italy) that shows the potential uses of MI to understanding the volatile evolution. I present a model showing the dynamic of the magma based on MI. This study also discusses the origin of anomalous MI and which MI provide the best information. The final chapter is dedicated to test the applicability of the new Linkam TS1400XY heating stage. I was able to show how this new microthermometric tool is capable of homogenizing MI at high temperature and to quench MI to a homogeneous glass state.
Ph. D.

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23

Koegelenberg, Corne. "Experimental evidence for sulphide magma percolation and evolution : relevant to the chromite bearing reefs of the Bushveld Complex." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20043.

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Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Pt mineralization within the Bushveld Complex is strikingly focused on the chromitite reefs, despite these horizons being associated with low volumes of base metal sulphide relative to Pt grade. Partitioning of Pt (Dsil/sulp) from silicate magma into immiscible sulphide liquid appears unable to explain Pt concentrations in chromitite horizons, due to the mismatch that exists between very large R factor required and the relevant silicate rock volume. Consequently, in this experimental study we attempt to gain better insight into possible Pt grade enhancement processes that may occur with the Bushveld Complex (BC) sulphide magma. We investigate the wetting properties of sulphide melt relevant to chromite and silicate minerals, as this is a key parameter controlling sulphide liquid percolation through the cumulate pile. Additionally, we have investigated how fractionation of the sulphide liquid from mono-sulphide-solid-solution (Mss) crystals formed within the overlying melanorite might affect sulphide composition and Pt grades within the evolved sulphide melt. Two sets of experiments were conducted: Firstly, at 1 atm to investigate the phase relations between 900OC and 1150OC, within Pt-bearing sulphide magma relevant to the BC; Secondly, at 4 kbar, between 900OC to 1050OC, which investigated the downwards percolation of sulphide magma through several layers of silicate (melanorite) and chromitite. In addition, 1atm experiments were conducted within a chromite dominated chromite-sulphide mixture to test if interaction with chromite affects the sulphide system by ether adding or removing Fe2+. Primary observations are as follows: We found sulphide liquid to be extremely mobile, the median dihedral angles between sulphide melt and the minerals of chromitite and silicate layers are 11O and 33O respectively. This is far below the percolation threshold of 60O for natural geological systems. In silicate layers sulphide liquid forms vertical melt networks promoting percolation. In contrast, the extremely effective wetting of sulphide liquid in chromitites restricts sulphide percolation. Inter-granular capillary forces increase melt retention, thus chromitites serve as a reservoir for sulphide melt. Sulphide liquid preferentially leaches Fe2+ from chromite, increasing the Fe concentration of the sulphide liquid. The reacted chromite rims are enriched in spinel end-member. This addition of Fe2+ to the sulphide magma prompts crystallization Fe-rich Mss, decreasing the S-content of sulphide melt. This lowers Pt solubility and leads to the formation of Pt alloys within the chromitite layer. Eventually, Cu-rich sulphide melt escapes through the bottom of the chromitite layer. These observations appear directly applicable to the mineralized chromitite reefs of the Bushveld complex. We propose that sulphide magma, potentially injected from the mantle with new silicate magma injections, percolated through the silicate cumulate overlying the chromitite and crystallized a significant volume of Fe-Mss. Chromitite layers functioned as traps for percolating, evolved, Cu-, Ni- and Pt-rich sulphide liquids. This is supported by the common phenomenon that chromitites contain higher percentages of Ni, Cu and Pt relative to hanging wall silicate layers. When in contact with chromite, sulphide melt is forced to crystallize Mss as it leaches Fe2+ from the chromite, thereby further lowering the S-content of the melt. This results in precipitation, as Pt alloys, of a large proportion of the Pt dissolved in the sulphide melt. In combination, these processes explain why chromitite reefs in the Bushveld Complex have Pt/S ratios are up to an order of magnitude higher that adjacent melanorite layers.
AFRIKAANSE OPSOMMING: Pt mineralisasie in die Bosveld Kompleks is kenmerkend gefokus op die chromatiet riwwe, alhoewel die riwwe geassosieer is met lae volumes basismetaal sulfiedes relatief tot Pt graad. Verdeling van Pt (Dsil/sulp) vanaf silikaat magma in onmengbare sulfiedvloeistof is klaarblyklik onvoldoende om Pt konsentrasies in chromatiet lae te verduidelik, a.g.v. die wanverhouding wat bestaan tussen ‘n baie groot R-faktor wat benodig word en die relatiewe silikaat rots volumes. Gevolglik, in die eksperimentele studie probeer ons beter insig kry oor moontlike Pt graad verhogingsprosesse wat plaasvind in die BK sulfied magma. Ons ondersoek die benattingseienskappe van sulfied vloeistof relevant tot chromiet- en silikaat minerale, omdat dit die sleutel maatstaf is vir die beheer van sulfied vloeistof deursypeling deur die kumulaat opeenhoping. Addisioneel het ons ook ondersoek hoe die fraksionering van sulfied vloeistof vanaf MSS kristalle, gevorm binne die hangende melanoriet muur, moontlik die sulfied samestelling en Pt graad binne ontwikkelde sulfied smelt kan beïnvloed. Twee stelle van eksperimente is gedoen: Eerstens, by 1 atm om ondersoek in te stel oor fase verwantskappe tussen 900OC en 1150OC, binne ‘n Pt-verrykte sulfied magma samestelling relevant tot die BK; Tweedens, by 4 kbar, tussen 900OC tot 1050OC, wat die afwaartse deursypeling van sulfied magma deur veelvuldige lae van silikaat minerale en chromatiet. Addisionele 1 atm eksperimente is gedoen binne ‘n chromiet gedomineerde chromiet-sulfied mengsel, om te toets of interaksie met chromiet die sulfied sisteem affekteer deur Fe2+ te verwyder of by te dra. Primêre observasies is soos volg: Ons het bevind sulfiedsmelt is uiters mobiel, die mediaan dihedrale hoek tussen sulfiedsmelt en minerale van chromiet en silikaat lae is 11O en 33O onderskydelik. Dit is ver onder die deursypelings drumpel van 60O vir natuurlike geologiese stelsels. In silikaatlae vorm die sulfiedsmelt vertikale netwerke wat deursypeling bevorder. Inteendeel, uiters effektiewe benatting van sulfiedsmelt binne chromatiete vertraag sulfied deusypeling. Tussen kristal kapilêre kragte verhoog smelt retensie, dus dien chromatiete as ‘n opgaarmedium vir sulfiedsmelt. S oorversadigte sulfied vloeistof loogsif Fe2+ vanuit chromiet en veroorsaak ‘n verhoging in Fe-konsentraie. Die gereageerde chromiet buiterante is daarvolgens verryk in Cr-spinêl eind-ledemaat. Die addisionele byvoeging van Fe2+ aan sulfied magma veroorsaak die kristalisasie van Fe-ryke Mss en verlaag dus die S-konsentrasie van die sulfied smelt. Dit verlaag Pt oplosbaarheid en lei tot die formasie van Py allooie binne-in chromatiete. Ten einde, ontsnap Cu-ryke sulfied smelt deur die onderkant van die chromatiet lae. Die observasies is direk van toepassing op die gemineraliseerde chromatiet riwwe van die Bosveld Kompleks. Ons stel voor dat sulfied magma, potensiaal ingespuit vanuit die mantel saam nuwe inspuitings van silikaat magma, deur die hangende silikaat kumulaat bo chromatiet lae deurgesypel het en ‘n betekenisvolle volume Fe-Mss gekristalliseer het. Chromatiet lae het gefunksioneer as lokvalle vir afwaartsbewegende, ontwikkelde, Cu-, Ni-, en Pt-ryke sulfied vloeistowwe. Dit word ondersteun deur die algemene verskynsel dat chromatiete hoër persentasies van Ni, Cu en Pt relatief teenoor die hangende muur silikaat lae het. Wanneer sulfied smelt in kontak is met chromiet, word dit geforseer om Mss te kristalliseer soos Fe2+ geloogsif word, waarvolgens die smelt se S konsentrasie verder verlaag word. Dit veroorsaak die presipitasie, as Pt allooie, van groot proporsies opgeloste Pt vanuit sulfied smelt. Deur die prosesse te kombineer, kan dit moontlik verduidelik word hoekom chromatiet riwwe in die Bosveld Kompleks Pt/S verhoudings veel hoër is as aanrakende melanoriet lae.

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Stechern, André [Verfasser]. "Decoding magma plumbing and geochemical evolution of active volcanoes of the Central Andes (North Chile) with petrological methods / André Stechern." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1074968824/34.

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25

Stepner, Daniel. "Source and Magma Evolution of the Tuff of Elevenmile Canyon, Stillwater Range, Clan Alpine and Northern Desatoya Mountains, Western Nevada." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36893.

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The tuff of Elevenmile Canyon (TEC) is a 25.1 Ma trachydacite to rhyolite intracaldera tuff produced by the largest of 6 Oligocene overlapping calderas that, along with related plutons, constitute the Stillwater Caldera Complex, one of the largest eruptions of the Western Nevada Volcanic Field during the mid-Tertiary ignimbrite flare-up. Typically crystal-rich with a mineral assemblage of plagioclase > quartz  sanidine > biotite ± hornblende and clinopyroxene, there are two discernable pumice types throughout the tuff: a lighter crystal-rich pumice and a darker, commonly aphyric pumice type. Rb-Sr and Sm-Nd isotopic compositions of pumice fragments and whole rock samples indicate an enriched mantle component (87Sr/86Srin = 0.70495 – 0.70535, Nd[t=25.1Ma] = -1.13 to -0.39) similar to that of coeval Cenozoic mafic lavas. Pb isotopes (206Pb/204Pbin = 19.042 – 19.168, 207Pb/204Pbin = 15.557 – 15.664) fall along a tight trend between the Northern Hemisphere Reference Line (Hart 1984) and an endmember similar to local granitic units. Major and trace element modelling support a source for the TEC derived from the mixing of anatectic melts of crustal rocks with intruded mantle-derived magmas similar to a local basaltic-andesite.

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Chevalier, Laure. "Evolution des conditions d’écoulement du magma et du dégazage dans les conduits éruptifs des volcans andésitiques : apports de la modélisation numérique." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU008/document.

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L'activité des volcans andésitiques, tels que le Mont St Helens (États-Unis), Montserrat (Antilles) ou encore le Merapi (Indonésie), alterne entre des périodes relativement calmes, avec coulées de lave et formation d'un dôme, et des événements explosifs parfois très violents. Prévoir les transitions entre ces deux régimes est essentiel pour assurer la sécurité des populations voisines, mais demeure actuellement un vrai défi. Or les données expérimentales et les observations de terrain montrent que l'explosivité du magma est étroitement liée à son contenu en gaz. L'objectif de cette thèse est d'améliorer notre compréhension de l'évolution de ce contenu en gaz et de son influence sur l'activité volcanique, en nous appuyant sur des simulations numériques, l'analyse de données expérimentales ainsi que sur l'interprétation de données de déformation enregistrées au Merapi.Une part importante de ce travail réside dans le développement et l'amélioration de modèles d'écoulement en 2D pour prendre en compte le dégazage dans la partie supérieure du conduit, en régime transitoire. Nous présentons un modèle d'écoulement du gaz en temps qui tient compte des pertes en gaz aux bords du conduit et à sa sortie, selon les conditions présentes dans la roche encaissante et le dôme. Nous proposons également une adaptation des modèles de conduit permettant de coupler complètement l'écoulement du gaz avec celui du magma pour étudier l'évolution des conditions dans le conduit en régime transitoire. À partir de simulations de l'évolution du dégazage lors de l'emplacement d'un dôme, nous identifions les para-mètres contrôlant les pertes en gaz. Nos résultats montrent que ces pertes sont extrêmement sensibles à l'évolution de la perméabilité du magma et des gradients de pression autour du conduit en réponse au poids du dôme. La perméabilité du dôme a quant à elle peu d'influence. Au cours de la croissance du dôme, les pertes en gaz diminuent en profondeur. En haut du conduit, la pression du gaz augmente de quelques dizaines de MPa. Ces effets sont associés à une augmentation de l'explosivité du magma et de l'aléa volcanique en cas d'effondrement du dôme.Bien que la perméabilité du magma exerce un fort contrôle sur la perte de gaz, comme l'ont montré nos résultats, son évolution dans le conduit est peu contrainte. Les lois de perméabilité utilisées actuellement ne sont pas en accord avec l'ensemble des mesures réalisées sur des échantillons de magmas riches en silice. Dans le but d'améliorer notre compréhension du développement de la perméabilité dans le conduit, nous avons cherché à éclaircir le lien entre perméabilité, conditions d'écoulements, et caractéristiques géométriques du réseau de bulles connectées. Nous proposons une formulation du seuil de percolation, moment exact où le magma devient perméable compatible avec un grand nombre d'échantillons naturels et expérimentaux. Nous présentons aussi une nouvelle loi de perméabilité en accord avec la plupart des observations existantes, que nous avons intégrée à notre modèle 2D de dégazage. Nos résultats montrent qu'en fonction du nombre de bulles dans le magma et de la distribution de leurs tailles, l'importance des pertes en gaz et par conséquent les conditions d'écoulement dans le conduit varient d'effusives à explosives.Enfin, afin d'évaluer l'utilité des données de déformation pour suivre l'évolution des conditions d'écoulement, nous utilisons des modèles d'écoulement simples couplés à de la déformation élastique en 3D pour retrouver la déformation observée au sommet du Merapi peu avant l'éruption de 2006. Bien que ces modèles permettent de mieux comprendre les déplacements observés, le peu de données, associé à la complexité géologique et rhéologique du sommet, ainsi qu'à celle des processus physiques intervenant dans le conduit font qu'il est difficile de contraindre les conditions d'écoulement grâce à la déformation dans ce cas précis
At silicic volcanoes, such as Mount St Helens (United States), Montserrat (British West Indies), or Merapi (Indonesia), periods of relative quiescence, with lava flows and dome emplacement, alternate with explosive, sometimes very violent events. Forecasting the effusive/explosive transitions, which is essential for the safety of nearby populations, remains currently a real challenge. However, experimental as well as field observations provide evidence that magma gas content is a major clue for understanding explosivity. This thesis, based on numerical simulations, experimental samples analysis, as well as on the interpretation of ground deformation data recorded at Merapi volcano, aims at improving our understanding of gas loss evolution, and its impact on the eruptive regime.A major part of this work consisted in developing and improving 2D axisymmetric conduit flow models for integrating gas loss in transient conditions. We provide a time-dependent model for gas flow in the upper conduit, that accounts for gas loss both at the conduit walls and at its top, depending on conditions in the surrounding rock and dome. We also propose an adaptation of conduit flow models allowing for full coupling between magma and gas flow in 2D that should be used to further investigate flow conditions evolution during transient regimes. From time-dependent gas flow simulations in the case of an effusive dome emplacement, we identify controlling parameters for gas loss. Our results provide evidence that gas loss is extremely sensitive to the evolution of magma permeability and of pressure gradients around the conduit due to dome loading, whereas, contrary to the common idea, dome permeability has almost no influence. Along with dome growth, gas loss decreases at depth, thus causing an increase in the magma gas content. At the top of the conduit, this results in an increase in gas pressure by a few tens of MPa, thus increasing the likelihood of magma explosivity and hazard in the case of a rapid decompression due to dome collapse.Although magma permeability plays a major role for gas extraction, as revealed by our results, its evolution within the conduit is poorly constrained. Currently used permeability laws fail in reassembling the whole dataset of permeability measurements from natural and experimental silicic samples. In order to improve our understanding of permeability development in the conduit, we worked on linking permeability and flow conditions with geometrical parameters that characterise the connected bubble network, based on experimental samples analysis. We propose an expression for the percolation threshold, i.e. the very moment when magma becomes permeable, that succeeds in classifying a wide dataset of natural and experimental samples. We also develop a new permeability law that reassembles most of the existing observations, and implement it within our gas flow 2D model. Results show that depending on the number of bubbles within the magma and on their size distribution, gas loss and then magma flow conditions evolve from effusive to explosive conditions.Eventually, we evaluate the applicability of monitoring flow conditions from observed ground deformation by using simplified conduit flow models, coupled with elastic deformation in 3D, to interpret ground deformation recorded in the near field at Merapi a few days before the 2006 eruption. Although conduit flow models provide important clues for interpreting observed displacements, the sparsity of field observations together with the complexity of the volcano summit geology, rheology and processes happening in the conduit make it very complex to constrain flow conditions from observed deformation

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Day, Simon John. "The geology of the Hypersthene Gabbro of Ardnamurchan Point and implications for its evolution as an upper crustal basic magma chamber." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6510/.

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The Hypersthene Gabbro of Ardnamurchan Point is formed by an outer Marginal Border Group ( MBG ) and a younger Inner Series (IS). The MBG is a single large intrusion which corresponds to a high - melt - percentage magma chamber. The IS is dominated by numerous gabbronorite sheet intrusions which formed a large low - melt - percentage magma body. The country rocks around the MBG show polyphase metamorphism. An early (Ml) phase of high-grade metamorphiam was followed by sudden cooling and then by hydrothermal metamorphism ( M2 ), related in part to the emplacement of the IS. The sudden cooling was caused by self - propagation of tensile fracture networks containing vigorously convecting hydrothermal fluids. The fracture networks were initiated by tectonic fracturing. The fractures networks also propagated into the MBG and partly preserved the magma chamber boundary layer formed during Ml. The contact of the MBG was approximately stationary during Ml. Wall - rock melting occurred in an episodic process triggered by movement on concentric inward - dipping normal faults due to fluctuations in magma pressure. The heat flux Q(_m) in the boundary layer was approximately equal to the heat flux Qc in the adjacent wall rocks. The preservation of the end – M1 instantaneous metamorphic thermal gradient in the country rocks by the subsequent sudden cooling allows direct measurement of Q(_c) and hence of Q(_m) (8 - 40Wm(^-2)) and other parameters of the boundary layer of the MBG magma chamber. The interior of the MBG magma chamber was probably just stably stratified but cooling at the chamber walls produced density currents and slow mixing between the layers. The chamber was not well - mixed: variations in previous crustal contamination of the magmas have been preserved. The IS shows evidence for interstitial melt expulsion related to the formation of igneous lamination. Hydrothermal circulation in the IS, at up to 1000ºC, produced oxidation of the rocks and may have led to the formation of hydrous melts.

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Mäkisalo, A. (Anssi). "Geological characterization of anorthositic rocks in the Otanmäki intrusion, central Finland:constraints on magma evolution and Fe-Ti-V oxide ore genesis." Master's thesis, University of Oulu, 2019. http://jultika.oulu.fi/Record/nbnfioulu-201903201346.

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Abstract. The 2.06 Ga Otanmäki intrusion in central Finland is a differentiated mafic intrusion hosting stratabound Fe-Ti-V oxide ore. The ore occurs as <1–200-m-wide lenses in a heterogeneous zone comprising different gabbro varieties and anorthosite. Anorthosite forms ubiquitous amoeboid-shaped inclusions a few meters in diameter, constituting a significant component in the ore-bearing part of the intrusion. The anorthositic rocks have not been studied earlier in detail and their role in the geological history of the intrusion is not well understood. The purpose of this Master’s thesis is to characterize the anorthositic rocks by means of mapping and geochemical and minerochemical methods, compare them to other mafic rocks in the Otanmäki intrusion and corresponding mafic intrusions globally and study their role in the magmatic evolution and Fe-Ti-V oxide ore genesis. A total of 20 thin sections were prepared for petrographic microscopy and 64 EPMA analyses were made to determine the plagioclase composition. The geochemical data include 18 ICP-OES/ICP-MS analyses and 58 portable XRF measurements. Pre-existing data, which include 941 bedrock observation points, 139 thin sections, 197 geochemical analyses and 110 electron microanalyses, were utilized as well as historical maps and drill core logs by the mining company Rautaruukki Oy. Based on the mapping campaign carried out in 2017–2018, a 1:50 000 geological map of the Otanmäki intrusion covering 20 km² and a related stratigraphical column are presented. Detailed maps in 1:200 scale, which are based on aerial drone photography from anorthosite-bearing areas, were also compiled. A revised nomenclature for the Otanmäki intrusion is presented, in which the intrusion is divided into three tectonic blocks: Otanneva, Otanmäki, and Vuorokas. All these blocks comprise three major stratigraphical units: the Lower Zone, Ore Zone and Upper Zone. Furthermore, fine-grained marginal amphibolites are reported from two locations. Based on the mineralogical observations and major and trace element data, the anorthositic rocks represent strongly differentiated plagioclase adcumulates and are cognate to the Otanmäki intrusion. Crystallization of the Ore and Upper Zones has likely included one or several periods of plagioclase buoyancy, enabling accumulation of plagioclase crystals in the roof part of the magma chamber. Parts of the massive roof anorthosite sank gravitationally into the lower parts of the magma chamber as variably solidified autoliths and were deposited on a semi-solidified substratum. The sinking was likely affected by Fe-Ti-oxide crystallization and subsequent decrease in the density of the residual melt. The genesis of the Fe-Ti-V oxide ore is suggested to have been affected by gravitational movements of partially solidified cumulate slurry towards a subsided magma chamber center. At least parts of these movements postdate the deposition of the anorthositic autoliths. The occurrence of anorthositic autoliths bears many similarities with the Skergaard and Sept Iles mafic intrusions.Otanmäen intruusion anortosiittisten kivien geologinen karakterisointi ja merkitys magmaattisessa evoluutiossa sekä Fe-Ti-V-oksidimalmin synnyssä. Tiivistelmä. Kainuussa sijaitseva Otanmäen intruusio on differentioitunut mafinen intruusio, jossa esiintyy kerrosmyötäistä Fe-Ti-V-oksidimalmia. Malmi ilmenee <1–200 metriä leveinä linsseinä heterogeenisessä vyöhykkeessä, joka koostuu eri gabrotyypeistä sekä anortosiitista. Anortosiitti muodostaa muutamia metrejä halkaisijaltaan olevia runsaslukuisia, muodoltaan vaihtelevia sulkeumia. Sulkeumat ovat merkittävä komponentti intruusion malmia sisältävässä osassa, mutta niitä ei ole tutkittu tarkasti ja niiden merkitys intruusion geologisessa historiassa on osin epäselvä. Tämän pro gradu -tutkielman tarkoitus on karakterisoida anortosiittiset kivet geologisen kartoituksen sekä kokokivi- ja mineraalikemiallisten menetelmien avulla, verrata niitä intruusion muihin mafisiin kiviin sekä vastaaviin intruusioihin globaalisti ja tutkia niiden merkitystä magmaattisen evoluution ja Fe-Ti-V-oksidimalmin synnyn kannalta. Työtä varten valmistettiin 20 ohuthiettä, joista tehtiin mikroskooppisten tutkimusten lisäksi 64 elektronimikroanalyysiä plagioklaasin koostumuksen selvittämiseksi. Geokemiallinen aineisto sisältää 18 ICP-OES/ICP-MS analyysiä sekä 58 kannettavalla XRF-analysaattorilla tehtyä koostumusmittausta. Lisäksi hyödynnettiin aikaisempien tutkimusten aineistoja, joihin kuuluu 941 kallioperähavaintopistettä, 139 ohuthiettä, 197 kokokivigeokemiallista analyysia, 110 elektronimikroanalyysia sekä Rautaruukki Oy:n laatimia karttoja ja kairasydänraportteja Otanmäen intruusiosta laadittiin vuosina 2017–18 suoritetun kartoitustyön perusteella 20 km²:n kattava, 1:50 000-mittakaavainen geologinen kartta sekä stratigrafiapylväs. Lisäksi laadittiin 1:200-mittakaavassa yksityiskohtaisia geologisia karttoja anortosiittisia sulkeumia sisältäviltä alueilta hyödyntäen drone-ilmakuvausta. Työssä esitetään uusi, yhtenäistetty nimistö Otanmäen intruusiolle. Intruusio jaetaan kolmeen tektoniseen lohkoon: Otanneva, Otanmäki ja Vuorokas. Intruusiolohkot sisältävät kolme magmaattisen stratigrafian pääyksikköä: alavyöhyke, malmivyöhyke ja ylävyöhyke. Lisäksi intruusion reunoilla esiintyy kahdessa kohtaa hienorakeisia amfiboliittisia kiviä. Mineralogisten havaintojen sekä pää- ja hivenalkuainekoostumuksen perusteella anortosiittiset kivet ovat voimakkaasti differentioituneita plagioklaasiadkumulaatteja, jotka ovat syntyneet samasta magmasta muiden intruusion kivien kanssa. Malmi- ja ylävyöhykkeiden kiteytymisen aikana plagioklaasi on ainakin ajoittain kellunut magmassa. Tämä on mahdollistanut plagioklaasikiteiden kasautumisen magmasäiliön yläosaan. Osa tästä yläosan massiivisesta anortosiitista upposi takaisin magmasäiliön alempiin osiin vaihtelevasti kiinteytyneinä autoliitteina, jotka kerrostuivat osin jähmettyneeseen kumulaattikerrokseen. Oksidimalmin kiteytyminen ja siitä seurannut tiheyden lasku jäännössulassa ovat todennäköisesti vaikuttaneet autoliittien uppoamiseen. Fe-Ti-V-oksidimalmin syntyyn on vaikuttanut osittain kiteytyneiden kumulaattien valuminen kohti magmasäiliön vajonnutta keskustaa. Malmivyöhykkeessä tapahtuneet magmaattiset liikunnot ovat tapahtuneet ainakin osittain anortosiittisten autoliittien kerrostumisen jälkeen. Autoliittien osalta Otanmäen intruusiolla on merkittäviä yhteneväisyyksiä Skaergaardin ja Sept Ilesin intruusioihin.

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Richardson, Jacob Armstrong. "Modeling the Construction and Evolution of Distributed Volcanic Fields on Earth and Mars." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6136.

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Magmatism is a dominant process on Earth and Mars that has significantly modified and evolved the lithospheres of each planet by delivering magma to shallow depths and to the surface. Two common modes of volcanism are present on both Earth and Mars: central-vent dominated volcanism that creates large edifices from concentrating magma in chambers before eruptions and distributed volcanism that creates many smaller edifices on the surface through the independent ascent of individual magmatic dikes. In regions of distributed volcanism, clusters of volcanoes develop over thousands to millions of years. This dissertation explores the geology of distributed volcanism on Earth and Mars from shallow depths (~1 km) to the surface. On long time scales, distributed volcanism emplaces magmatic sills below the surface and feeds volcanoes at the surface. The change in spatial distribution and formation rate of volcanoes over time is used to infer the evolution of the source region of magma generation. At short time scales, the emplacement of lava flows in these fields present an urgent hazard for nearby people and infrastructure. I present software that can be used to simulate lava flow inundation and show that individual computer codes can be validated using real-world flows. On Mars, distributed volcanism occurs in the Tharsis Volcanic Province, sometimes associated with larger, central-vent shield volcanoes. Two volcanic fields in this province are mapped here. The Syria Planum field is composed three major volcanic units, two of which are clusters of 10s to >100 shield volcanoes. This area had volcanic activity that spanned 900 million years, from 3.5-2.6 Ga. The Arsia Mons Caldera field is associated with a large shield volcano. Using crater age-dating and mapping stratigraphy between lava flows, activity in this field peaked at ~150 Ma and monotonically waned until 10-90 Ma, when volcanism likely ceased.

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Needy, Sarah Katherine. "Tracking the Evolution of Mid Cenozoic Silicic Magma Systems in the Southern Chocolate Mountains Region, California Using Zircon Geochemistry and Quartz and Zircon Geothermometry." Thesis, Connect to resource online, 2009. http://hdl.handle.net/1805/1953.

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Thesis (M.S.)--Indiana University, 2009.
Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Andrew P. Barth, Gabriel Filippelli, Jeffery Wilson. Includes vitae. Includes bibliographical references (leaves 62-64).

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Shoemaker, Kurt A. "THE TECTONOMAGMATIC EVOLUTION OF THE LATE CENOZOIC OWYHEE PLATEAU, NORTHWESTERN UNITED STATES." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1082580947.

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Amann, Méderic. "Evolution du magmatisme et du métasomatisme dans une marge passive pauvre en magma durant l'initiation de l'accrétion océanique : exemple de la marge fossile de la Platta (Alpes suisses) et comparaison avec le système actuel Ibérie-Terre Neuve." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAH014/document.

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Les parties distales des marges passives pauvres en magma représentent la transition complexe entre les domaines continentaux et océaniques. Ces zones encore peu étudiées sont pourtant des endroits clefs pour comprendre les processus impliqués durant les premiers stades de l’accrétion océanique, et plus particulièrement ceux du magmatisme et du métasomatisme. Durant ces premiers stades, ces deux processus sont gouvernés par l’exhumation mantellique. L’interaction entre les liquides magmatiques, les roches du manteau et les fluides marins vont affecter le régime thermique de la marge. De par le monde, seulement deux Transitions Océan-Continent (TOC) ont pu bénéficier d’investigations scientifiques poussées et constituent naturellement les deux sites d’études de cette thèse, à savoir, les marges actuelles conjuguées d’Ibérie-Terre Neuve du sud de l’Atlantique Nord ainsi que les marges fossiles de la Platta et de Tasna, fragments de TOCs de la Téthys Alpine Jurassique. En combinant les études de terrain ainsi que les investigations minéralogiques, pétrologiques et géochimiques, nous avons pu contraindre trois processus clefs se déroulant dans les TOCs. (i) La percolation de liquide magmatique imprégnant le manteau sous-continental hérité dans les marges Ibérie-Terre Neuve permet une refertilisation de ces marges distales. (ii) La transition géochimique visible entre les basaltes des TOCs et les basaltes de dorsales océaniques peut s’appréhender par la fusion partielle du manteau sous-continental refertilisé. (iii) Le rôle des fluides hydrothermaux, ayant des températures comprises entre 60°C et 190°C, joue un rôle sur le métasomatisme de la lithosphère en produisant une intense serpentinisation et rodingitisation, respectivement du manteau sous-continental en exhumation et des dykes basaltiques. Ces températures étant cohérentes avec une exhumation mantellique au niveau du plancher océanique
Distal parts of magma-poor rifted margins represent a complex transition between continental and oceanic domains. These areas remain poorly understood while being a key-place to unravel magmatic and metasomatic processes involved during the first stages of oceanization. At this time, these processes are enhanced by mantle exhumation, and the interaction between melts, mantle rocks and fluids affect the thermal regime of the margin. So far, only two Ocean-Continent Transitions (OCT) have been particularly investigated, namely the present-day Iberia Newfoundland conjugate margins and the fossil analog Platta-Tasna nappes, remnants of the Jurassic Alpine-Tethys OCTs. Studies presented in this Ph.D. thesis have been focused on these two margins. Here, by combining field-works, petrological, mineralogical and geochemical investigations, we have unraveled in OCTs three key-points: (i) The deep porous-flow melt percolation impregnating the long-lived inherited subcontinental mantle in Iberia-Newfoundland margins allow the refertilization of these distal domains; (ii) The geochemical transition depicted from OCT-basalts towards MOR-basalts can be explained by the partial melting of the refertilized subcontinental mantle; (iii) The role of active hydrothermal fluids, on both the exhumed mantle and basalt dikes, lead to the serpentinisation and the rodingitization respectively, at temperature ranging between 60°C and 190°C. These temperatures being consistent with the ongoing mantle exhumation towards near-seafloor conditions

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Cáceres, Acevedo Francisco [Verfasser], and Bettina [Akademischer Betreuer] Scheu. "The role of nano- to millimetre sized crystals on the dynamic evolution of shallow silica-rich magma : implications for volcanic eruptions / Francisco Cáceres Acevedo ; Betreuer: Bettina Scheu." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1216039429/34.

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34

Davarpanah, Armita. "Magmatic Evolution of the Eocene Volcanic Rocks of the Bijgerd Kuh E Kharchin Area, Uromieh-Dokhtar Zone, Iran." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/geosciences_theses/19.

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Composition and texture of the Middle and Late Eocene volcanic, volcaniclastic, and volcanic-sedimentary rocks in the Bijgerd-Kuh e Kharchin area, in the Uromieh-Dokhtar zone northwest of Saveh, Iran, suggest the complexity of the magmatic system that involved multiple eruptions from one or more sources. Hydrated volcanic fragments in hyaloclastic rocks, and the presence of a sequence of shallow and intermediate-depth marine microfossils, suggest that the Middle Eocene units were erupted in a marine basin. The bimodal volcanism of the Late Eocene is distinguished by the presence of four alternating sequences of hyaloclastite lava and ignimbrite. The REE patterns show spatial homogeneity and temporal heterogeneity in the composition of all the Late Eocene sequences, suggesting origination of magma from varying sources that erupted at different times. The trace element distributions of the hyaloclastites and ignimbrites are compatible with those evolved through fractional crystallization of the lower and upper continental crust, respectively.

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Epin, Marie-Eva. "Evolution morpho-tectonique et magmatique polyphasée des marges ultra-distales pauvres en magma : la transition océan-continent fossile de l'Err et de la Platta (SE Suisse) et comparaison avec des analogues actuels." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAH013/document.

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Cette thèse a pour but d’étudier l’évolution morpho-structurale et magmatique des marges distales pauvres en magma ainsi que leur réactivation. Cette étude est focalisée sur les marges fossiles distales de la Téthys Alpine. L’étude de la réactivation de ces domaines (l’Err et la Platta, Suisse) montre que les chevauchements alpins réactivent principalement d’anciennes structures de rift. L’Err peut ainsi être restaurée et correspond à un ancien domaine de croute hyper-amincie caractérisé par un système de failles de détachement qui évolue en séquence et conduit à la rupture continentale et à l’exhumation du manteau. La Platta correspond à un domaine de manteau sous continental exhumé associé à une augmentation des additions magmatiques syn-tectoniques dans les parties distales. Ce domaine est interprété comme la relique d’une structure en dôme coiffée par une faille de détachement et recoupée par des failles normales favorisant la mise en place de magma et de fluides. L’approche utilisée a permis de mieux contraindre l’architecture d’une marge distale pauvre en magma et de discuter les processus de formation et de la réactivation des limites de plaque
The aim of this study is to investigate the morpho-structural and magmatic evolution of magma-poor distal rifted margins, as well as their reactivation. This study is focused on the fossil distal margins of the Alpine Tethys. The study of the reactivation of these domains, (Err and Platta, Switzerland) shows that alpine thrusts principally reworked former rift structures. The Err nappe can be restored as a hyper-extended domain characterized by a system of detachment faults with a complex architecture evolving in-sequence and leads to the continental crust separation and the exhumation of mantle. The Platta nappe corresponds to a subcontinental exhumed mantle domain associated to an increase of syn-tectonic magmatic additions oceanwards. The distal domain is interpreted as the relic of a dome-shaped structure capped by a detachment fault and crosscut by latter normal faults facilitating the emplacement of basalts and fluid circulations. The approach developed in this thesis enabled a better understanding of one distal and ultra-distal magma-poor rifted margin, as well as to discuss processes related to the formation and reactivation of plate boundaries

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Mamberti, Marc. "Origin and evolution of two distinct Cretaceous oceanic plateaus accreted in Western Ecuador (South America) : Petrological, geochemical and isotopic evidence." Phd thesis, Université Joseph Fourier (Grenoble), 2001. http://tel.archives-ouvertes.fr/tel-00688387.

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La géologie de l'Equateur se distingue de celle du reste des Cordillères andines par la présence de terrains océaniques qui s'accrètent successivement à la marge depuis la fin du Crétacé jusqu'au Paléocène. Ces terrains exotiques sont constitués de fragments de deux plateaux océaniques du Crétacé inférieur (123 Ma) et supérieur (90 Ma) et de plusieurs arcs insulaires (100 à 40 Ma). Dans la Cordillère occidentale, le plateau crétacé inférieur et les terrains océaniques du crétacé supérieur (plateau et arcs insulaires) s'accrètent respectivement à 85-80 Ma et 70-65 Ma. Le plateau océanique daté à 123 Ma est constitué: (i) de cumulats basiques et ultrabasiques (série de San Juan) et (ii) de basaltes en coussins et de dolérites massives recoupés par des petites intrusions de gabbro sub-doléritique. Les cumulats forment une série continue depuis des dunites et wehrlites jusqu'à des gabbros à clinopyroxène. Basaltes, dolérites et gabbros présentent tous les caractères de basalte de plateau océanique (OPB; MgO = 7%; spectres de terres rares plats, pas d'anomalie négative en Nb et Ta). Les compositions isotopiques (Nd et Pb) des cumulats et de l'ensemble basalte-dolérite sont identiques et démontrent que toutes ces roches dérivent d' une source mantellique enrichie. Les picrites et les basaltes enrichis ou non en MgO, associés à des dolérites et des gabbros, représentent des témoins accrétés du plateau océanique crétacé supérieur caraïbe. Les picrites (MgO -20 %) sont appauvries en terres rares légères, peu radiogéniques en Pb et caractérisées par des eNd élevés (+8 à +10). Les basaltes riches en MgO (9-10%) sont enrichis en terres rares légères. La géochimie en éléments traces des basaltes pauvres en MgO est identique à celle d'OPB. Par contre, les rapports isotopiques du Pb des basaltes, riches en MgO ou non, sont très élevés indiquant que toutes ces laves dérivent d'une source enrichie de type HIMU, caractère commun à tous les basaltes du plateau caraïbe .

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Fuchs, Parveen [Verfasser]. "Petrogenesis of basanite-phonolite series of an oceanic intraplate volcano : combining experimental data and field observations ; experimental constraints on the magma storage conditions and melt evolution of the Cumbre Vieja volcano (La Palma, Canary Islands) / Parveen Fuchs." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1070284955/34.

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38

Wei, Wei. "Characteristics of the late Mesozoic tectonic evolution of the South China block and geodynamic implications : Multi-approach study on the Qingyang-Jiuhua, Hengshan and Fujian coastal granitic massifs." Phd thesis, Université d'Orléans, 2013. http://tel.archives-ouvertes.fr/tel-01058791.

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The vast distribution and long duration of the Late Mesozoic magmatism in the eastern part of South China presents a unique case in the world. This offers a natural laboratory to study the process of magma genesis, the magma emplacement mode, the relationship between magmatism and tectonics, the geodynamic role on the magma emplacement and lithospheric evolution. Since 50's, particularly 90's of the last century, geoscientists have made important efforts in geological cartography and carried out numerous studies with remarkable scientific achievements, building a solid background to understand the tectonic evolution of the South China Block (SCB). However, certain fundamental questions mentioned above remain unsolved and/or are in hot debate. In order to make progress in these scientific issues, we have carried out in a multi-disciplinary study in the Late Mesozoic Qingyang-Jiuhua massif, Hengshan massif and Fujian coastal zone according to their distance with respect to the paleo subduction zone of the Paleo-Pacific plate, the ages of granitic massifs and related tectonics, including field observation on the structure geology, micro-observation on thin section, U-Pb dating on monazite, AMS, paleomagnetism, gravity modeling and P condition concern the granite emplacement. In the view of deformation in these granitic massifs and their country rocks, mode and influence of regional tectonics on the emplacement, though each studied zone reveals its distinguished characteristics, they show some intrinsic and common relationships between them. With our new results and integrating previous data, in this thesis, we discuss the tectonic context of emplacement of these Late Mesozoic magmatic massifs and the geodynamic evolution of the SCB., We propose a 3-step geodynamic model: (1) during 145-130 Ma period, the Paleo-Pacific plate subducted northwestwardly, the West Philippines micro-continent, approaching to SCB, important subduction-related arc volcanism was produced in the coastal areas of Southeast China coast (Zhejiang-Fujian-Guangdong), forming a back-arc extension tectonic system in SCB; (2) during 130-110 Ma period, due to the collision between the West Philippines microcontinent and SCB, the compressional tectonic structures were developed in the Changle-Na'ao coastal zone, producing ductile deformation zones. However, the inland of the eastern part of SCB was under a NW-SE extensional tectonic regime; (3) during 105-90 Ma period, a new subduction zone was developed in the SE flank of the West Philippines micro-continent, the subducting slab reached the Changle-Nan'ao tectonic belt, with the possible break-off of slab, the asthenospheric ascent was responsible for the important emplacement of plutonic massifs and dykes. The tectonics of the eastern part of SCB was characterized by a general extensional system in this period. This tectonic pattern has been significantly disturbed by the Oligocene-Eocene opening of the South China sea,and the Miocene shortening of the SCB margin in Taiwan. Of course, this model should be improved by more geological, geophysical and geochemical investigations.

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Tang, Eng Hoo Joseph. "The Petrogenesis Of The Station Creek Igneous Complex And Associated Volcanics, Northern New England Orogen." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15902/1/Joseph_Tang_Thesis.pdf.

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The Station Creek Igneous Complex (SCIC) is one of the largest Middle-Late Triassic plutonic bodies in the northern New England Orogen of Eastern Australia. The igneous complex comprises of five plutons - the Woonga Granodiorite (237 Ma), Woolooga Granodiorite (234 Ma), Rush Creek Granodiorites (231 Ma) and Gibraltar Quartz Monzodiorite and Mount Mucki Diorite (227 Ma respectively), emplaced as high-level or epizonal bodies within the Devonian-Carboniferous subduction complex that resulted from a westward subduction along the east Australian margin. Composition of the SCIC ranges from monzogabbro to monzogranite, and includes diorite, monzodiorite, quartz monzodiorite and granodiorite. The SCIC has the typical I-type granitoid mineralogy, geochemistry and isotopic compositions. Its geochemistry is characteristics of continental arc magma, and has a depleted-upper mantle signature with up to 14 wt% supracrustal components (87Sr/86Srinitial = 0.70312 to 0.70391; Nd = +1.35 to +4.9; high CaO, Sr, MgO; and low Ni, Cr, Ba, Rb, Zr, Nb, Ga and Y). The SCIC (SiO2 47%-76%) has similar Nd and Sr isotopic values to island-arc and continentalised island-arc basalts, which suggests major involvement of upper mantle sourced melts in its petrogenesis. SCIC comprises of two geochemical groups - the Woolooga-Rush Greek Granodiorite group (W-RC) and the Mount Mucki Diorite-Gibraltar Quartz Monzodiorite group (MMD-GQM). The W-RC Group is high-potassium, calc-alkalic and metaluminous, whereas the MMD-GQM Group is medium to high potassium, transitional calc-alkalic to tholeiitic and metaluminous. The two geochemical groups of the SCIC magmas are generated from at least two distinct sources - an isotopically evolved Neoproterozoic mantle-derived source with greater supracrustal component (10-14 wt%), and an isotopically primitive mafic source with upper mantle affinity. Petrogenetic modeling using both major and trace elements established that the variations within respective geochemical group resulted from fractional crystallisation of clinopyroxene, amphibole and plagioclase from mafic magma, and late fractionation of alkalic and albitic plagioclase in the more evolved magma. Volcanic rocks associated with SCIC are the North Arm Volcanics (232 Ma), and the Neara Volcanics (241-242 Ma) of the Toogoolawah Group. The major and trace element geochemistry of the North Arm Volcanics is similar to the SCIC, suggesting possible co-magmatic relationship between the SCIC and the volcanic rock. The age of the North Arm Volcanics matches the age of the fractionated Rush Creek Granodiorite, and xenoliths of the pluton are found within epiclastic flows of the volcanic unit. The Neara Volcanics (87Sr/86Sr= 0.70152-0.70330, 143Nd/144Nd = 0.51253-0.51259) differs isotopically from the SCIC, indicating a source region within the HIMU mantle reservoir (commonly associated with contaminated upper mantle by altered oceanic crust). The Neara Volcanics is not co-magmatic to the SCIC and is derived from partial melting upper-mantle with additional components from the subducting oceanic plate. The high levels emplacement of an isotopically primitive mantle-derived magma of the SCIC suggest periods of extension during the waning stage of convergence associated with the Hunter Bowen Orogeny in the northern New England Orogen. The geochemical change between 237 to 227 Ma from a depleted-mantle source with diminishing crustal components, to depleted-mantle fractionate, reflects a fundamental change in the source region that can be related to the tectonic styles. The decreasing amount of supracrustal component suggests either thinning of the subduction complex due to crustal attenuation, leading to the late Triassic extension that enables mantle melts to reach subcrustal levels.

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40

Tang, Eng Hoo Joseph. "The Petrogenesis Of The Station Creek Igneous Complex And Associated Volcanics, Northern New England Orogen." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15902/.

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The Station Creek Igneous Complex (SCIC) is one of the largest Middle-Late Triassic plutonic bodies in the northern New England Orogen of Eastern Australia. The igneous complex comprises of five plutons - the Woonga Granodiorite (237 Ma), Woolooga Granodiorite (234 Ma), Rush Creek Granodiorites (231 Ma) and Gibraltar Quartz Monzodiorite and Mount Mucki Diorite (227 Ma respectively), emplaced as high-level or epizonal bodies within the Devonian-Carboniferous subduction complex that resulted from a westward subduction along the east Australian margin. Composition of the SCIC ranges from monzogabbro to monzogranite, and includes diorite, monzodiorite, quartz monzodiorite and granodiorite. The SCIC has the typical I-type granitoid mineralogy, geochemistry and isotopic compositions. Its geochemistry is characteristics of continental arc magma, and has a depleted-upper mantle signature with up to 14 wt% supracrustal components (87Sr/86Srinitial = 0.70312 to 0.70391; Nd = +1.35 to +4.9; high CaO, Sr, MgO; and low Ni, Cr, Ba, Rb, Zr, Nb, Ga and Y). The SCIC (SiO2 47%-76%) has similar Nd and Sr isotopic values to island-arc and continentalised island-arc basalts, which suggests major involvement of upper mantle sourced melts in its petrogenesis. SCIC comprises of two geochemical groups - the Woolooga-Rush Greek Granodiorite group (W-RC) and the Mount Mucki Diorite-Gibraltar Quartz Monzodiorite group (MMD-GQM). The W-RC Group is high-potassium, calc-alkalic and metaluminous, whereas the MMD-GQM Group is medium to high potassium, transitional calc-alkalic to tholeiitic and metaluminous. The two geochemical groups of the SCIC magmas are generated from at least two distinct sources - an isotopically evolved Neoproterozoic mantle-derived source with greater supracrustal component (10-14 wt%), and an isotopically primitive mafic source with upper mantle affinity. Petrogenetic modeling using both major and trace elements established that the variations within respective geochemical group resulted from fractional crystallisation of clinopyroxene, amphibole and plagioclase from mafic magma, and late fractionation of alkalic and albitic plagioclase in the more evolved magma. Volcanic rocks associated with SCIC are the North Arm Volcanics (232 Ma), and the Neara Volcanics (241-242 Ma) of the Toogoolawah Group. The major and trace element geochemistry of the North Arm Volcanics is similar to the SCIC, suggesting possible co-magmatic relationship between the SCIC and the volcanic rock. The age of the North Arm Volcanics matches the age of the fractionated Rush Creek Granodiorite, and xenoliths of the pluton are found within epiclastic flows of the volcanic unit. The Neara Volcanics (87Sr/86Sr= 0.70152-0.70330, 143Nd/144Nd = 0.51253-0.51259) differs isotopically from the SCIC, indicating a source region within the HIMU mantle reservoir (commonly associated with contaminated upper mantle by altered oceanic crust). The Neara Volcanics is not co-magmatic to the SCIC and is derived from partial melting upper-mantle with additional components from the subducting oceanic plate. The high levels emplacement of an isotopically primitive mantle-derived magma of the SCIC suggest periods of extension during the waning stage of convergence associated with the Hunter Bowen Orogeny in the northern New England Orogen. The geochemical change between 237 to 227 Ma from a depleted-mantle source with diminishing crustal components, to depleted-mantle fractionate, reflects a fundamental change in the source region that can be related to the tectonic styles. The decreasing amount of supracrustal component suggests either thinning of the subduction complex due to crustal attenuation, leading to the late Triassic extension that enables mantle melts to reach subcrustal levels.

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41

CHAKRABORTY, SUVANKAR. "THE GEOCHEMICAL EVOLUTION OF ALKALINE MAGMAS FROM THE CRARY MOUNTAINS, MARIE BYRD LAND, ANTARCTICA." Bowling Green State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1174187928.

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42

Heath, Emily. "Genesis and evolution of calc-alkaline magmas at Soufriere volcano, St Vincent, Lesser Antilles arc." Thesis, Lancaster University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360643.

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Soufriere of St. Vincent is the most active subaerial volcano in the Lesser Antilles arc, and is composed of basalts and basaltic andesites. Eruptive style has tended to alternate between predominantly effusive and explosive, although magma compositions show no systematic variations with time. New Ar-Ar and 14C dates help to constrain the geological evolution of the (- 0.6 Ma) volcano. Parental, possibly primary, magmas at Soufriere had MgO contents exceeding 12 wt.% (mg# 75) and were probably nepheline-normative. They may be representative of the parental magmas of the calc-alkaline suites of the Lesser Antilles arc. The source mantle probably resembled that of N-MORB, prior to metasomatic enrichment by hydrous slab-derived fluids, containing contributions from subducted sediments and oceanic crust. Parental magmas last equilibrated with the mantle at - 17 kbar pressure, with temperatures greater than 1130·C and f02 exceeding FMQ +1. Near-primary basaltic lavas were only erupted during the earliest (Pre-Somma) phase of volcanism. Basaltic andesites (and occasional andesites) were produced by fractionation of 01 + spinel + cpx + plag ± opx over a range of crustal pressures (5-10kbar), at temperatures mainly in the range 1000 - 1l00·C. The total amount of crystallization was some 76 wt. %, and amphibole was apparently not a fractionating phase. There is conflicting evidence as to the pre-eruptive water contents of Soufriere magmas; phenocryst compositions suggest H20 > 3 wt. %, whereas various projections into phase diagrams are more consistent with relatively anhydrous magmas. Magma mixing did not apparently play a significant role in the evolution of most Soufriere magmas, and fractional crystallization was not accompanied by crustal assimilation, judging from trace element and Sr-Nd isotope systematics. New U-Th mineral isochrons suggest that magmas resided for tens of thousands of years within the crust, which requires rather stable thermodynamic conditions in the magma chamber(s) beneath Soufriere.

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Moore, Nicole E. DeBari Susan M. "Origin and geochemical evolution of mafic magmas from Mount Baker in the northern Cascade arc, Washington : probes into mantle and crustal processes /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=345&CISOBOX=1&REC=14.

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Dunn, Natalie Kirsty. "Petrogenesis of hybrid porphyry pipes and evolution of alkaline magmas in the Kanabeam Igneous Complex, Southern Namibia." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/4195.

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Includes bibliography.
The linear Kuboos Bremen Igneous Province (KBIP) stretches 270km from the South African Atlantic coast north-eastwards into southern Namibia, and was emplaced at approximately 500Ma. One central complex within the KBIP is the Kanabeam Igneous Complex (KIC) where practically all the rock types found in the province are represented and include nepheline syenites, quartz syenites as well as granites. In addition to these plutonic phases a number of late stage, xenolith rich porphyry pipes were emplaced, exploiting contact zones between earlier plutons. Xenolith types include gabbro possibly derived from unexposed deeper parts of the KIC, syenites (more proximal components of the KIC), trachytes from an inferred overlying volcanic edifice, basement granites, gneisses and metasediments as well as Nama Group sediments. Petrographicl examination in the porphyries has releaved that there are numerous minerals out of textual equilibrium, including olivine, pyroxene and plagioclase. Other minerals such as biotite, amphibole and alkali feldspar appear more stable.

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45

Wingrove, Dennis. "Early mixing in the evolution of alkaline magmas chemical and oxygen evidence from phenocrysts, Royal Society Range, Antarctica /." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1116257410.

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46

Wingrove, Dennis Warden. "Early Mixing in the Evolution of Alkaline Magmas: Chemical and Oxygen Evidence from Phenocrysts, Royal Society Range, Antarctica." Bowling Green State University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1116257410.

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47

Isom, Shelby Lee. "Compositional and Physical Gradients in the Magmas of the Devine Canyon Tuff, Eastern Oregon| Constraints for Evolution Models of Voluminous High-silica Rhyolites." Thesis, Portland State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10606618.

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Large-volume silicic ignimbrites erupt from reservoirs that vary in composition, temperature, volatile content and crystallinity. The 9.7 Ma Devine Canyon Tuff (DCT) of eastern Oregon is a large-volume (>250 km³), compositionally zoned and variably welded ignimbrite. The ignimbrite exhibits heterogeneous trace element compositions, variable volatile content and crystallinity. These observations were utilized in the investigation into the generation, accumulation and evolution of the magmas composing the DCT. Building off previous research, pumices were selected from the range of trace element compositions and analyzed with respect to crystallinity, mineral abundances and assemblages. The DCT displays a gradational trace element enrichment and decrease in crystallinity from least evolved, dacite, at ∼22% crystals to most evolved high-silica rhyolite at 3% crystals. Two distinct mineral populations of feldspar and clinopyroxene were identified in previous work, one belonging to the rhyolitic magma and the other to the dacitic magma. Volatile content derived from melt inclusion Fourier Transform Infrared (FTIR) spectrometer analysis revealed an increase in water content from 1.2 to 3.7 wt.% in the most evolved rhyolite. The DCT exhibits low and variable δ¹⁸O signatures, 4.52‰ to 5.76‰, based on δ¹⁸O values measured on quartz and sanidine. Low δ¹⁸O signatures of all DCT rhyolites suggest the incorporation of hydrothermally altered crust into the melt. Furthermore, quartz phenocrysts from all high-silica rhyolite groups display dark oscillatory zoned cores and Ti-rich bright rims.

These data provide insight into how these magmas were generated and subsequently stored in the crust. Commonalities of petrographic and compositional features among rhyolites, especially the zoning characteristics of quartz phenocrysts, exclude the possibility of storage and evolution in multiple reservoirs. Envisioning a scenario where all magmas are stored within a single reservoir prior to eruption and assuming rhyolites A and D are the product of partial melting. The mixing of A and D rhyolites produced rhyolite B, and subsequent mixing of intermediate rhyolite B and end-member rhyolite D generated rhyolite C. However, some trace element inconsistencies, between mixing model and observed intermediate rhyolites suggest a secondary process. Post mixing, rhyolites B and C require some modification by fractional crystallization to account for LREE and other inconsistencies between mixed models and observed rhyolites. Finally, the origin of the dacite is likely through mixing of group D rhyolite and an intrusive fractionated basalt, which could have led to the eruption of the Devine Canyon Tuff.

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Alonso, Perez Raquel. "The role of garnet in the evolution of hydrous, calc-alkaline magmas : an experimental study at 0.8 - 1.5 GPa /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16999.

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Guernina, Souad. "Formation and evolution of granite magmas from migmatites : an example from the Ashuanipi subprovince in the Superior province, Québec /." Thèse, Chicoutimi : Montréal : Université du Québec à Chicoutimi ; Université du Québec à Montréal, 2007. http://theses.uqac.ca.

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Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, avec la collaboration et la participation de l'Université du Québec à Montréal, 2007.
La p. de t. porte en outre: Thèse présentée à l'Université du Québec à Chicoutimi comme exigence partielle de doctorat en ressources minérales. CaQCU Bibliogr.: f. 259-289. Document électronique également accessible en format PDF. CaQCU

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Bouilhol, Pierre. "Structural, petrological and geochemical constraints on transfer and evolution of arc magmas in the mafic-ultramafic Sapat Complex (Kohistan; Northern Pakistan) /." Zürich : Eidgenössische Technische Hochschule, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18081.

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Dissertations / Theses on the topic 'Evolution of magma'

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